Search Documents

By D. Maddocks

"IntroductionThe greater part of the iron ore industry in Canada is located along the Labrador-Quebec border on a geological formation known as the Labrador trough. The Labrador trough is a 700 · mile long geosynclinal segment composed of folded and faulted Proterozoic sediments, volcanics and intrusives, extending from Gagnon, Quebec, to the north west tip of Ungava Bay. This geosyncline can be divided into three parts (Fig. 1).The northern unmined part, extending from southern to northern Ungava Bay, is a low grade metamorphosed iron formation.The iron deposits of the central region, represented by Schefferville, are hematite-limonite ores formed by oxidation and leaching of an unmetamorphosed taconite formation. Average iron content of the ore is greater than 540Jo for direct shipping and 50% for plant feed.The deposits of the southern section (Carol Lake, Wabush, Mt. Wright, Gagnon) extend from just north of Carol Lake to Gagnon and is a metamorphosed silica-iron oxide (specular hematite and magnetite) formation averaging plus 30% iron.The mineral wealth of this area was first observed by Father Louis Babel about 1870 and again by Dr. A.P. Low of the Geological Survey of Canada in 1894. However, the remote location hindered development until after 1945. First production of direct shipping ore from Schefferville was in 1954. Production at Carol Lake commenced in 1962.This area now accounts for sixty million long tons (61 Mt) per year of processed iron ore products as follows:This chapter will concentrate on pelletizing and agglomeration as experienced at the Iron Ore Company's Carol Lake operation. However, whenever possible, reference will be made to alternate methods, procedures, equipment, etc."

Jan 1, 1989

By Ltd. (CYMCO) Technology Center Yunnan Metallurgical Group Co., S. Jian, T. Song, J. D. Miller

"As sulfide zinc ore deposits become exhausted, nonsulfide zinc ore deposits become the other resource for zinc production. However, flotation for zinc recovery from nonsulfide deposits is much more difficult than the flotation of sphalerite from sulfide deposits and may become an option for zinc production only if a suitable processing technology is developed. In this regard, research efforts are being devoted to the flotation of nonsulfide zinc oxide minerals. Some common methods which have been used for the flotation of zinc oxide minerals include sulfidization-flotation, activation, and direct flotation with anionic and cationic collectors. The traditional flotation techniques have low efficiency and difficulty in separation and recovery of the zinc minerals from gangue minerals, for example, smithsonite (ZnCO3) from other carbonate gangue minerals and hemimorphite (Zn4Si2O7 (OH)2·H2O) from silicate gangue minerals. In this study potassium lauryl phosphate was evaluated as a collector for the flotation of nonsulfide zinc minerals. Results from contact angle and microflotation experiments at pH 6–9 show that hemimorphite (Zn4Si2O7 (OH)2·H2O) can be floated from quartz and that smithsonite (ZnCO3) can be floated from calcite. However, when dodecylamine, which is a common collector reported in literature for the flotation of nonsulfide zinc minerals, was used as collector, no significant difference between nonsulfide zinc minerals and gangue minerals was observed at any pH value. Initial evaluation suggests that potassium lauryl phosphate is effective at low concentration and may be a promising collector for zinc oxide mineral flotation.INTRODUCTIONBefore the twentieth century, zinc was mainly produced from nonsulfide ores (Large, 2001; Gilg, Boni, & Cook, 2008). With the development of differential flotation processes in the late 19th century major production switched from nonsulfide zinc sources to sulfide zinc ores (Hitzman, Reynolds, Sangster, Allen, & Carman, 2003; Gilg et al., 2008). However, as it is becoming more difficult to find new sulfide ores, recovery from nonsulfide deposits is being considered. Nonsulfide flotation for zinc recovery is much more difficult than the flotation recovery of sphalerite from sulfide deposits and may become an option for zinc production if a suitable technology is developed. Zinc and lead oxide ores are difficult to beneficiate ores due to their similar floatability with gangue, high solubility in water, and the influence of slimes (Fa, Miller, Tao, & Li, 2005). In order to improve the performance of oxidized minerals, lots of effort is being devoted to this field of study (Ejtemaei & Mahdi, 2014)."

Jan 1, 2016

By Z. Luo, China University of Mining & Technology, C. Duan

"The magnetic separation removal rate of pyrite could be improved effectively by increasing the susceptibility of pyrite. The electromagnetic characteristics and absorption response performance of high-sulfur fine coal were studied in strengthening the susceptibility of pyrite. In the process of treating the sample through the microwave, electromagnetic energy could be converted into heat energy due to dielectric loss and magnetic loss. The RL(dB) was evaluate the performance of absorption response of coal. The microwave improved the susceptibility was in ultra-high frequency region, which is the most natural resonance. The absorption fine coal to microwave was strengthened and microwave energy was improved by adding the magnetite powder with double loss characteristics as the microwave absorber. The dielectric properties and permeability characteristics of the fine coal trend were investigated by maxing magnetite powder. The microwave absorption in different coal thickness was surveyed through the reflection of energy loss.INTRODUCTIONMicrowave desulfurization is one of the most important research directions (Haque, 1999; Makul, Rattanadecho, & Agrawal, 2014; Su, Tang, Zhang, Jing, & Bai, 2014). The working principle of microwave absorption response can be briefly described as the interaction of the sample with microwave energy, which will result in the microwave energy converting into heat energy loss (Keangin & Rattanadecho, 2013). For specific samples, the polarization effect includes multiple polarization mechanisms(Meikap, Purohit, & Mahadevan, 2005). Different polarization mechanisms have different occurrence time and dominant mechanisms. Meantime, energy consumption will be occurred during the process of polarization effect (Chelgani & Jorjani, 2011; Rowson & Rice, 1990) . The absorption of microwave energy in the fine coal is a process of electromagnetic response (Znamenácková, Lovás, Mockovciaková, Jakabský, & Briancin, 2005). Microwave transfers the electromagnetic waves into the heat energy by microwave dielectric loss and magnetic loss for achieving the absorption of microwave energy in the treatment of samples (Lee, Kim, Kim, Chung, & Kim, 2004). The additive magnetic medium is Fe3O4 belonging to microwave energy absorber of double loss medium (Uslu, Atalay, & Arol, 2003)."

Jan 1, 2016

By F. H. Edmunds

LLOYDMINSTER is the centre of a well developed agricultural area, lying on the Alberta-Saskatchewan interprovincial boundary in Township Fifty. The surrounding country is gently undulating, without any notable topographic features, but twenty-two miles to the north the North Saskatchewan river, and thirty miles to the south the Battle river, have cut deep valleys. In the spring of 1934, a wild-cat well (Lloydminster Gas Company's No. 1 well) was successful in striking a large flow of gas at a depth o 1,974 ? feet. The gas was piped into the town, a short distance south, and Lloyd-minster became the first Saskatchewan town to be served with natural gas. Following this discovery, other wells were sunk and, up to the present, thirteen wells have been drilled m what is here designated the Lloydminster area. Ten of these wells are in Saskatchewan and three in Alberta. Seven were successful in obtaining gas, three oil, and three have been unsuccessful. The area tested by this drilling is about eight thousand acres, six thousand of which can be considered as proved gas or oil land. To the south and west of Lloydminster, in the Province of Alberta, there are several areas in which oil and gas have been discovered. The Wainwright field lies nearly fifty miles to the southwest; Battleview, where recently gas has been discovered, is thirty miles west-southwest; and the Ribstone area is about thirty miles south and a little west. At Ribstone, a number of wells were drilled some years ago and there is a small production of oil. The data relating to the wells in the Lloydminster area that are recorded in this paper are taken from the records of the several companies operating in the field. The names of these companies are given on the map and on the type stratigraphic section (Figures 1 and 2). The author wishes to record his appreciation to Mr. R. H. Shaw and Mr. 0. C. Yates, both of Lloyd-minster, for much valuable information; also to Mr. E. Swain, of the Department of Natural Resources, Regina, with whom the writer has visited the field on several occasions, and who, by his enthusiasm and encouragement, has done much to forward the development of the area. The well samples were examined at Ottawa by officers of the Borings Division of the Geological Survey of Canada, who also made the interpretations of the logs. Frequent references will be made to the work of Dr. G. S. Hume, of the Geological Survey, and the writer would like to pay tribute here to his work.

Jan 1, 1940

By K. S. Coley, G. A. Irons, T. Kaneyasu

"It is very important to reveal the lime dissolution mechanism in steelmaking slag, to promote its dissolution without calcium fluoride, which is now almost forbidden for use in most industrialized countries. In this research, the purpose was focused on the development of an experimental method to measure the mutual diffusivity of Ca2+ under the condition of lime dissolution into slag. By forming diffusion couples using a ""vacuum slag aspirating technique"", the method was established. The following mutual diffusivities of Ca2+, in CaO-SiO2-FeO slag systems, imitating oxygen steelmaking slag, were determined using this method:4.1*10-10 m2/s at 1400°C for 27wt.%CaO-53wt.%SiO2-20wt.%FeO slag,4.3* 10-10 m2/s and at 1400°C for 20wt.%CaO-40wt.%SiO2-40wt.%FeO slag, and 1.3*10-10 m2/s at 1250°C for 20wt.%CaO-40wt.%SiO2-40wt.%FeO slag.It was also verified that, if the basicity and ferrite content of the bulk slag are low, then a calcium silicate film forms on the lime surface, and drastically deters the lime dissolution."

Jan 1, 2004

By K. M. Ed

AN explosive is a solid or liquid substance which, when fired by some means, changes into a gaseous product occupying a volume very much greater than its original volume. The great speed at which this change takes place causes the explosive to exert a sudden blow on adjacent material. It is this action which is effective in blasting operations when the explosive, confined in a shot-hole, is fired. All explosives are similar in one respect, in that the change into the gaseous state is accompanied by the production of hot gases or flame. This results from the rapid combustion of the solid or liquid ingredients. Ex-plosives differ greatly, however, in the speed at which the reaction takes place. Black blasting powder, for instance, reacts comparatively slowly, hence the flame persists for an appreciable length of time. High explosives, on the other hand, react much more quickly; consequently, the flame is of much shorter duration. In 'closed-light' or 'gaseous' coal mines, the use of ordinary explosives is generally prohibited, due to their inherent ability to ignite gas or coal-dust by reason of the flame which they produce when fired. For instance, black blasting powder, which produces a flame of long duration, is not ordinarily considered safe to use in such mines; neither are ordinary dynamites, as their flames, while shorter than that of black blasting powder are, nevertheless, of sufficient temperature and duration to cause ignition of fire-damp or coal-dust. For this reason, specially formulated high explosives, called 'permitted' explosives, should invariably be used in such mines.

Jan 1, 1940

By J. Mrozowski, R. Kurowski, A. Chmielarz, Z. Szolomicki

PbSO4 is a commonly encountered component of the materials used in lead recycling (e.g. battery paste) and in by-products of metallurgical processes (e.g. residues from zinc hydrometallurgy, dust from copper smelting). Smelting of battery paste results in SO2 emission and in generation of significant amounts of hazardous ‘white slag’. Those adverse phenomena can be eliminated by removal of sulphur from the paste. Lead-bearing by-product materials are of polymetallic character with usually low Pb content, which makes lead recovery technologically difficult and uneconomic. However it can be successfully achieved by extraction of lead sulphate from solid phase with triethylenetetramine (TETA) water solutions. That compound has capability for selective solvation of a whole lead sulphate molecule. Virtually pure lead carbonate can be precipitated by means of saturation of lead-loaded aqueous TETA solution with carbon dioxide, and complete regeneration of the extractant is achieved by fixing of sulphate ion into gypsum through operation of calcium hydroxide suspension. The paper presents results of the lab and pilot scale studies into process of battery paste desulphurisation and recovery of lead from the residue of zinc calcine leaching.

Jan 1, 2014

By Isabel C. B Rodrigues, Flávia D. Reis, Versiane A. Leão, Rosa M. F. Lima

Attention has been focused in recent decades upon the precipitation of metal sulphides from acid mine drainage (AMD) and pregnant leach solutions, due to the advantages of the sulphide precipitation process over traditional methods employing hydroxides. The aim of this work was thus to explore technologies for copper precipitation using either Na2S or biogenic sulphide. The recovery of copper sulphide was improved when the initial pH of the solution containing each metal was 4 or excess sulphide was employed. In such, a condition the removal efficiency was 99.9%, corresponding to a residual level of 0.1mg/L for copper in solution. Kinetic parameters for precipitation were determined from the particle size distributions using the method of moments, where the growth and nucleation rates, as well the agglomeration kernel, were calculated. The biogenic sulphide was a suitable alternative to sodium sulphide for copper removal as either sodium sulphide and biogenic sulphide can be utilized to precipitate such a metal allowing the effluent to be compliant with environmental legislation.

Jan 1, 2014

By F. Habashi

Lead is an ancient metal, has been produced to-date from its ores exclusively by pyrometallurgical route. The process suffers from high operating cost and excessive pollution problems. Extensive research has been going on since the beginning of the twentieth century to find a non-polluting process for its production and a solution for its complex refining scheme. It has been assumed correctly that the hydrometallurgical route should be the most promising. Pilot plants have been constructed and operated for a reasonable periods, but no process has proved to be satisfactory. As a result, a number of smelters and refineries have been shut down. The present review analyses the situation and suggests that the best route to treat lead sulfide concentrates is by leaching with fluoroboric acid, HBF4, containing ferric fluoroborate, Fe(BF4)3, and electrolyzing the solution in a diaphragm cell - - a process recently invented by Italian metallurgists. In this process, any silver present in the concentrate remains in the residue together with elemental sulfur and can be recovered by known methods.

Jan 1, 2008

By Edward Martinez

Due to its unique properties, chrysotile asbestos is used in many diversified applications. In recent years, a better understanding of the structure and properties of chrysotile has evolved due to the research efforts of many investigators. A summary of the results of some of these investigations is given. An attempt is made to show the relationships between the properties of chrysotile and its crystal structure. Examples taken from the literature are cited in which methods have been developed for modifying the properties to improve the performance of asbestos in some applications. These include the effect of pH on the positive zeta potential and the addition of sodium silicate to improve filtration characteristics. The dehydroxylation and formation of forsterite when chrysotile is heated are also discussed.

Jan 1, 1966

By Ifeanyichukwu Nweke

"Aluminium rolling processing from ingots to cold rolled coils comes with a lot of challenges especially in controlling defective products in casting, hot mill and cold mill operations. Hence this study focused on reducing defects at mills and cast-house using six sigma approaches. The use of six sigma approach will help the production experts to determine the gap between its operation and world class process. Practical data from First Aluminium Rolling mills were presented and analysed and mini improvement projects were proposed based on organisation need to achieve excellence. This study encourages aluminium alloy industries to pursue process improvement projects on the basis of analysis on data obtained from their shop floor, hence ensuring that through this, recovery is improved and cost of poor quality is reduced.INTRODUCTION Engineer Bill Smith while working at Motorola in 1986 introduced a new concept in which a set of techniques and tools are used for process improvement by controlling variations (defects). These tools and techniques are explained by an acronym DMAIC. D DEFINE the problem M MEASURE the variables in the problem A ANALYSE the variables of the problem I IMPLEMENT and verify the solution to the problem C CONTROL the solution to sustain it Most times in six-sigma approach, variations in the process that results in defects and customers’ dissatisfaction are targeted at 3.4 defects per million opportunities. There are numerous methods six sigma application use to achieve quality results and innovative strategies. Improving the quality of process through these methods helps identify and reduce variations which paves way for organisational excellence. In this study, it is encouraged to use six sigma techniques to improve aluminium rolling operations and other aluminium processing activities, the benefits of such improvement concept include: • Satisfy the voice of the customer (VOC) • Minimise costs • Maximise Profits • Build Good Team • Implement Profitable Project"

Jan 1, 2018

By M. E. Bilir

In this paper, we review cases in which dramatic and visual swelling problems are experienced in underground structures. Swelling rocks have caused many problems in underground engineering projects. They pose severe problems to the design, construction and maintenance of underground openings. If an appropriate integrated design procedure, which proceeds from exploration, tests, analyses and realistic assumptions of swelling behavior, is used during the design stage, the execution of the project can be completed without any serious delays or dramatic design changes. The case histories were subdivided into three classes that include tunnels, underground coal mines and others. For the evaluation of cases, the surrounding rocks, swelling minerals, water inflow, swelling test results and swelling problems were considered. The main purpose of this review is to inform the reader about potential problems with swelling phenomenon and to emphasize the rehabilitation and extensive cost which are encountered due to the lack of necessary integrated design approaches.

Aug 1, 2013

By Zhen Lei

In Alberta, Canada, heavy industrial projects are constructed using a prefabrication approach: spools and pipes are produced in the factory, and are assembled into modules that are transported to the industrial plants for installation by mobile cranes. Planning the onsite mobile crane operations is critical to the project budget and schedule. However, due to the large magnitude of industrial projects, manual heavy lift planning is tedious, and the results are not particularly responsive to site changes. This paper introduces an integrated mobile crane management system developed by PCL Industrial Management Inc., in collaboration with the University of Alberta, which investigates crane location selection and path checking for field module assembly. The project information is stored in a database, and the proposed system retrieves data, performs the calculations, and records the results back to the database; the calculations involve automatically selecting locations for the mobile crane, considering the crane capacity, lifting range and utilization. Lift paths for modules are checked for feasibility based on selected locations, satisfying the site and crane configuration constraints, and crane walking paths are planned if needed. The designed system is tested in an industrial project to validate the effectiveness of the system.

Aug 1, 2013

By T. Abu Leil

A new class of ternary Mg-Sn-Ca alloys is being developed to address the dual demands of corrosion and creep resistance at service temperatures. While tin has proven to enhance the corrosion resistance, calcium is expected to significantly increase their creep resistance of binary magnesium alloys. Their effects in ternary magnesium alloys are not yet known. The series of alloys studied has Sn and Ca in the ranges 3-6% and 1¬2%, respectively. The results indicate that these alloys have two-phase structures with CaMgSn phase dispersed in a matrix that is predominantly a solid solution of magnesium. The corrosion behavior of these alloys has been investigated by means of salt spray tests and potentio-dynamic measurements. Creep behavior of these alloys was measured at a temperature of 135 C under an applied compressive stress of 85 MPa. Scanning Electron Microscopy with Energy Dispersive X-ray facility and X-ray Diffraction techniques were used to characterize the microstructures. The results indicate the prospect of designing alloys that can provide optimum combinations of corrosion and creep resistance by adjusting the relative compositions of Sn and Ca in the system.

Jan 1, 2006

By Nick Vayenas, Ming Cai, Hongbin Zhang Lorrie Fava, Enrique Acuña

"A hybrid methodology is proposed to improve the accuracy of Diesel Particulate Matter (DPM) concentrations simulated in a ventilation network model by using Computational Fluid Dynamics (CFD). DPM, as a primary concern for underground hard-rock mines, has been studied in two dominant numerical models, ventilation network solvers and computational fluid dynamics. Ventilation network solvers are efficient, but they are not able to provide three-dimensional DPM concentration contours and only accept area-average DPM data as input. CFD simulations are time-consuming, but generating DPM concentration results with high accuracy. Besides, both monitoring points and planes can be created in a CFD model, which can take both point data and area-average DPM data as input. The hybrid methodology is intended to combine the advantages of the two by using the CFD results to update the network model results at key locations. A field study was conducted in a dead-end heading in an underground gold mine in the United States. Real-time DPM monitors were used to collect data. A CFD model and a network model were built for the experiment area. The CFD model was calibrated to the experimental data. In the study presented here, results from a calibrated CFD model are converted to equivalent diesel emission rates in the ventilation network model at a shared outlet. The hybrid methodology is used to provide better input for the network model. INTRODUCTION Mine ventilation system is one of the most important parts for an underground mine. It not only provides fresh air to the personnel but also helps clear the contaminants generated from the diesel-powered equipment. For most underground metal and non-metal mines, diesel particulate matter is the main contaminant. It is also the focus of this paper."

Jan 1, 2019

By C. G. Anderson

Industrially proven and applied nitrogen species catalyzed (i.e. NSC) acidic pressure leaching has been utilized to treat a number of ores, concentrates and recycled materials. This versatile technology offers many advantages including low temperatures, low pressures, low capital costs, low operating costs, faster throughput and less costly materials of construction than conventional pressure oxidation. This paper will elucidate the application of this technology for production of gold, silver, palladium, rhodium, zinc, germanium, gallium, cobalt, copper and nickel. Recycled material applications will also be elucidated. In addition, details of an application for treatment of a refractory chalcopyrite copper and gold bearing ore will be presented and pertinent economics discussed.

Jan 1, 2004

By L. B. Tsymbulov, L. Sh. Tsemekhman, A. N. Golov

Gipronickel Institute, JS is developing a process of continuous converting of Nicontaining copper matte and concentrates resulting in the production of blister copper and fluid NiO-containing slag in a two-zone Vaniukov furnace. The process under development is an alternative for the existing technology of blister copper production in converters, the latter being characterized with insufficient sulphur utilization, low direct copper recovery and the production of inconvenient for further processing solid slag on the basis of NiO and NiFe20 4- The results of pilot testing on processing of copper concentrate obtained from high-grade matte (HGM) separation in the two-zone Vaniukov furnace with the hearth area of 11.4 m2 are presented.

Jan 1, 2007

By Steven D. Botts

The Antamina project, owned by BHP Billiton Plc, Mitsubishi Corporation, Noranda Inc., and Teck Cominco Ltd. , is a $2.3 billion copper/zinc project, located in the Ancash Department in Perú. The project consists of an open pit mine, a 70,000 ton per day concentrator, a 302 Km. long concentrate pipeline, port facilities, a new access road, power line, and town site. The project is designed to produce up to 1.5 million tonnes per year of copper and zinc concentrates over a 23-year project life, and will be the third largest producer of zinc and the seventh largest producer of copper in the world. This mega project is the largest mining investment in the country and, during its construction stage, was the most important construction project worldwide. On May 28th, 2001, Antamina commenced testing operations and four months later, it reached commercial production. Antamina was officially inaugurated on November 14th, 2001 by Peruvian president Alejandro Toledo. The construction stage of the project generated 8,000 direct jobs, with a peak of 10,000 employees, and 30,000 indirect jobs. The permanent workforce consists of approximately 1650 employees, the vast majority of which are Peruvian Nationals; around 30% of whom came from the department of Ancash where the deposit is located. Approximately 5,800 indirect jobs will be generated from the project. Independent sources state that Antamina will increase the Peruvian mining exports by 30% and Peruvian GDP by 1.4% within its first year of full operation in 2002. Since winning the privatization bid for the project in 1996, the company has implemented a successful approach to community development and environmental protection based on sustainable development principals. Throughout the development of the project, a number of initiatives have been undertaken to ensure full involvement of the local populations in community development activities and the company?s environmental program. Due to its size, difficult logistics, cultural considerations and financial aspects, the project has faced a number of unique challenges in the area of environmental protection and management of community interaction. Antamina has been innovative in its approach to these issues, and as a result, has set new standards in Perú for environmental and community management, and sustainable development.

May 1, 2002

By David Sanscartier, Elizaveta Petelina, Alexey Klyashtorin

This paper provides an overview of the radiological risk mitigation approach applied by the Saskatchewan Research Council (SRC) for the remediation of 35 legacy uranium mine sites in northern Saskatchewan where uranium exploration and extraction took place in the 1950–60s. Mining activities resulted in an irregular increase of the gamma radiation dose rate (up to 18 μSv/h). The radiological objectives for the sites include a gamma dose rate at a spot (<2.5 μSv/h above local background), and the dose rate averaged over a hectare (<1 μSv/h above local background). These objectives are generally achievable at the impacted sites through the installation of shielding soil cover. This method may be impractical for site areas with rough terrain (e.g., steep slopes) and/or difficult access. A risk assessment approach is applied to determine if these areas can be safely left uncovered or if additional mitigation measures should be implemented. The risk assessment approach is based on two factors: (i) the ambient radiation dose rates collected through gamma surveys, and (ii) actual land use data collected through various surveys of activities of local community members at the sites. Exposure scenarios based on four land uses are applied to estimate a potential annual dose load for members of the public. The estimated doses are compared with the criterion of 0.3 mSv/a recommended by the Canadian Guidelines for the Management of Naturally Occurring Radioactive Materials (NORM). If the criteria are not satisfied, a mitigation plan is developed, and post-remediation gamma levels are modelled using GIS tools to evaluate the performance of the proposed mitigations. The proposed approach allows the team to optimize resources for the site remediation so that public exposure to NORM are as low as reasonably achievable after remediation.

Jan 1, 2020

By Pan Zhao, Yan-Nan Wang, Fei-Long Liao, Can Cai, Kai-Song Wu

"What are the basic physical parameters and main geometric parameters that are capable of representing the microscopic characteristics of rock? How can these parameters be used to accurately describe the macroscopic mechanical behavior of rock? With such questions in view, and based on the microcosmic structure analysis of rock slices, this paper presents a rock skeleton-pore structure model, holding that rock's mechanical behavior depends on the properties of rock skeleton materials and the form, size and distribution pattern of pores. According to rock stress and deformation behaviors, and in line with the skeleton-pore structure model, an essential mechanics theory for rock is advanced. The assumption that the skeleton materials are incompressible in volume and an introduction of logarithmic strain, generate the relation between porosity and apparent strain. Then, the notion that positive damage and negative damage are represented in terms of porosity is put forward; threshold value of porosity is derived by the damage threshold value of apparent volume strain; a general damage variable of rock is obtained; eventually, with the skeleton-pore model as the groundwork, a global damage constitutive equation is developed, which, with definite physical significance and material parameters to be easily determined, is convenient to apply. It has been proved that the results calculated with this new equation are well in agreement with experimental results.INTRODUCTIONRock is a form of material that contains pores, cracks and skeletons. Skeletons are composed of particles and cements. Pores or cracks within rock actually undermine the assumption of material continuum in solid mechanics. Hence, grave errors — or even false results — are inevitable if some solid mechanics theory is quoted in the discussion of rock mechanics. Many researchers in the field of rock mechanics have attempted various remedies, but the outcome is far from satisfactory — a mechanics theory for rock, in its true sense, has not been established."

Jan 1, 2015